Saturday, June 30, 2007

O Captain! my Captain! our fearful trip is done;The ship has weathered every rack, the prize we sought is won;The port is near, the bells I hear, the people all exulting,While follow eyes the steady keel, the vessel grim and daring.But O heart! heart! heart!O the bleeding drops of red!Where on the deck my Captain lies,Fallen cold and dead.

June 18, 2007 -- A probe of the upper echelons of the human brain's chain-of-command has found strong evidence that there are not one but two complementary commanders in charge of the brain, according to neuroscientists at Washington University School of Medicine in St. Louis.

It's as if Captains James T. Kirk and Jean-Luc Picard were both on the bridge and in command of the same starship Enterprise.

In reality, these two captains are networks of brain regions that do not consult each other but still work toward a common purpose — control of voluntary, goal-oriented behavior. This includes a vast range of activities from reading a word to searching for a star to singing a song, but likely does not include involuntary behaviors such as control of the pulse rate or digestion.

So there you have it. The captains don't talk to each other. This article (of course) is in reference to the paper by Dosenbach and colleagues (2007),1 in which they described two distinct task-control networks:

A frontoparietal network included the dorsolateral prefrontal cortex and intraparietal sulcus. This network emphasized start-cue and error-related activity and may initiate and adapt control on a trial-by-trial basis. The second network included dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex. Among other signals, these regions showed activity sustained across the entire task epoch, suggesting that this network may control goal-directed behavior through the stable maintenance of task sets.

Scientists exploring the upper reaches of the brain's command hierarchy were astonished to find not one but two brain networks in charge, represented by the differently-colored spheres on the brain image above. ... The regions in each network talked to each other often but never talked to brain regions in the other network. [from the wustl "two captains" news release by M. Purdy]

Shouldn't they be talking to each other at some point?

These two independent networks appear to operate on different time scales and affect downstream processing via dissociable mechanisms. [from Dosenbach et al., 2007]

If they're not talking directly to each other2, how does the sustained control network communicate the need to adjust performance on a moment-to-moment basis, and how does making a mistake (for instance) engage the sustained control network?

For possible answers to those questions, one is drawn to a popular model of discrete regions for cognitive control3 and conflict monitoring (Botvinick et al., 2001), which has been discussed at Developing Intelligence. Interestingly, Botvinick and colleagues seem to have located the areas for errors/trial adjustments and the areas for sustained task performance in the opposite structures from Dosenbach et al. (2007) [...sort of]. Namely, the conflict monitoring hypothesis (see also Botvinick et al., 2004; Yeung et al., 2004) places "watching out for response conflicts" (e.g., naming the ink color here -- BLUE -- as in the Stroop task) and "watching out response gaffes" (e.g., saying "blue" instead of "red" to the word above) in the anterior cingulate cortex. These functions would be part of the frontoparietal network for Dosenbach et al. (2007). Meanwhile, for Botvinick et al., the dorsolateral prefrontal cortex (PFC) implements "control"4 on a trial-by-trial basis and maintains task set on a sustained basis. Similarly, as part of the frontoparietal network, the dorsolateral PFC is involved in implementing adaptive control on a trial-by-trial basis for Dosenbach et al. In the longer run, however, this latter scheme puts another network (anterior cingulate/frontal operculum/anterior PFC) in charge of maintaining task set.

How do these views relate to other recent studies that emphasize the brain's network properties? As reviewed in the June 15 PERSPECTIVES in Science, Neural Networks Debunk Phrenology:

The studies show that network interactions among anatomically discrete brain regions underlie cognitive processing and dispel any phrenological notion that a given innate mental faculty is based solely in just one part of the brain.

In contrast to the outdated(Fuster, 2000) Modular Paradigm (in which cognitive functions and the contents of cognition are localized in discrete regions [discrete networks??] dedicated to the specific functions and domains), Fuster has long supported the Network Paradigm where higher cortical functions are distributed across brain regions, showing extensive intersection and overlap. In this scheme, one neuron can be part of many networks.

Fuster's unique twist is his emphasis on "extensive intersection and overlap," particularly at the highest levels of the hierarchy [where things are most distributed, rather than orchestrated by a single "central executive"].

To be fair, novel approaches by the non-Fuster investigators (reviewed by Knight in the Debunking Phrenology commentary) include characterizing the nature of neuronal oscillations that synchronize activity across cortical regions [but even aspects of that research are notall that new, of course; the recent Science article by Womelsdorf, Singer et al. certainly builds on their prior work dating back to the late 80's-early 90's].

At the end of the day, however, a lot of time and effort and money is still spent in search of the captain(s).

2 But see this quote on page 11077: "The frontoparietal and cinguloopercular control networks were strongly intraconnected and quite separate from each other, suggesting that they carry out dissociable control functions. The networks may nonetheless communicate with each other."

4 It would be good to listen to The Faint's The Conductor (Thin White Duke Mix), but I couldn't find the mp3 online. Imagine "control control control control control control..." repeated 100 times to an electroclash beat. Other tracks available here, though.

Monday, June 25, 2007

A new article in PNAS identified two distinct task-control networks by "applying graph theory to resting state functional connectivity MRI data" (Dosenbach et al., 2007). A press release from Washington University in St. Louis includes this quote from one of the authors (Steven Petersen, Ph.D.):

To enhance their analysis [resting state functional connectivity MRI], Dosenbach and Petersen turned to graph theory, a branch of mathematics that visually graphs relationships between pairs of objects.

"A similar approach is used in the party game Six Degrees of Kevin Bacon," Petersen notes. "You use paired connections — appearances in the same movie, marital relationships — to go from one actor or actress to another until you've identified a chain of connections linking Kevin Bacon and another performer that wasn't immediately obvious."

How many degrees away are you?

Steven E. Petersen, Ph.D., the James S. McDonnell Professor of Cognitive Neuroscience and director of the Division of Neuropsychology in Neurology in the School of Medicine, was elected as a fellow of the American Association for the Advancement of Science (AAAS).Individuals are elected as AAAS fellows in recognition of their efforts toward advancing science or fostering applications that are deemed scientifically or socially distinguished.Reference

Dosenbach NU, Fair DA, Miezin FM, Cohen AL, Wenger KK, Dosenbach RA, Fox MD, Snyder AZ, Vincent JL, Raichle ME, Schlaggar BL, Petersen SE. (2007). Distinct brain networks for adaptive and stable task control in humans. PNAS 2007 Jun 18; [Epub ahead of print].Control regions in the brain are thought to provide signals that configure the brain's moment-to-moment information processing. Previously, we identified regions that carried signals related to task-control initiation, maintenance, and adjustment. Here we characterize the interactions of these regions by applying graph theory to resting state functional connectivity MRI data. In contrast to previous, more unitary models of control, this approach suggests the presence of two distinct task-control networks. A frontoparietal network included the dorsolateral prefrontal cortex and intraparietal sulcus. This network emphasized start-cue and error-related activity and may initiate and adapt control on a trial-by-trial basis. The second network included dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex. Among other signals, these regions showed activity sustained across the entire task epoch, suggesting that this network may control goal-directed behavior through the stable maintenance of task sets. These two independent networks appear to operate on different time scales and affect downstream processing via dissociable mechanisms.

Friday, June 22, 2007

Scared. Angry. Putting a one word label on the face to the left by pressing one of two buttons was an experimental task performed by participants in a recent study by Lieberman et al. (2007). That's the same as years of talk therapy, according to science writers and even Lieberman himself. For example,

Tell your troubles to a Guatemalan worry doll, place it beneath your pillow and, according to legend, those worries will be gone by morning. That’s just one example of the culture-spanning idea that putting problems into words can blunt those problems’ emotional impact. Centuries of thinkers—from Spinoza to William James to every psychologist who practices talk therapy—have recognized this peculiar power of language, according to UCLA psychologist Matthew Lieberman, PhD.

. . .

Using fMRI, the researchers found that when the participants labeled the faces’ emotions using words, they showed less activity in the amygdala—an area of the brain associated with emotional distress. At the same time, they showed more activity in the right ventral lateral prefrontal cortex...

...this suggests that verbalizing an emotion may activate the right ventral lateral prefrontal cortex, which then suppresses the areas of the brain that produce emotional pain. [because deciding whether a face is angry or scared is so emotionally wrenching.]

"[In talk therapy] we tend to focus primarily on content and enhanced understandings and changed understandings," said Lieberman. "But it’s not entirely irrelevant that they all involve putting feelings into words."

What was the study about? The researchers compared "affect labeling" (shown above) to other kinds of tasks to see which brain regions were specifically active when people pressed a button to indicate whether a facial expression conveyed fear or anger [for instance; "happy" and "surprised" were other possibilities, but these occurred only 20% of the time]. What were the other tasks? The five control conditions were "affect matching"(choosing which of two faces matches the expression of the target), "gender matching" (choosing which of two faces matches the gender of the target), "shape matching" (with simple geometric shapes) "gender labeling" (choosing the gender-appropriate name), and "observe affect" (just look at the emotional face without making a response). The most important contrast was affect labeling vs. gender labeling.

What were the results, and how should we interpret them? Mind Hacks is most certainly on the right track (bold emphasis mine):

The VLPFC increases its activity to dampen down the emotions triggered by the amygdala.

However, it's not clear whether this happens equally for both positive and negative emotions, as 80% of the faces in the study had expressions of anger or fear, while only 20% displayed happiness or surprise, so this data only really tells us about unpleasant feelings.

We know that observing emotion in others makes us more likely to feel the same thing ourselves, but it's not the same as experiencing an emotion 'first-hand', so we need to be a bit careful in assuming that this study fully represents the more everyday experience of talking about our emotions.

This experiment gives us a good understanding of the brain circuit involved reducing emotional impact via naming, but it doesn't tell us much about why this occurs.

This is one of the major drawbacks of neuroimaging studies. They often just redescribe an effect in terms of brain activity.

Yes. But that doesn't stop journalists from wild extrapolation (see blogosphere debate on the conflict between scientists vs. science journalists).

CHICAGO (Reuters) - Putting feelings into words makes sadness and anger less intense, U.S. brain researchers said on Wednesday, in a finding that explains why talking to a therapist -- or even a sympathetic bartender -- often makes people feel better.

They said talking about negative feelings activates a part of the brain responsible for impulse control.

"Anger." There. I wrote it. Press the right button. Do I feel better now? Do you?

You're scaring me now in the new yearYou're scaring me nowYou're scaring me nowOne word is a bomb in your handsOne word becomes a bomb in your handsOne word is a bomb in your hands-- Scrawl, One Word

Reference

Lieberman MD, Eisenberger NI, Crockett MJ, Tom SM, Pfeifer JH, Way BM. (2007). Putting feelings into words: affect labeling disrupts amygdala activity in response to affective stimuli. Psychol Sci. 18(5):421-8.Putting feelings into words (affect labeling) has long been thought to help manage negative emotional experiences; however, the mechanisms by which affect labeling produces this benefit remain largely unknown. Recent neuroimaging studies suggest a possible neurocognitive pathway for this process, but methodological limitations of previous studies have prevented strong inferences from being drawn. A functional magnetic resonance imaging study of affect labeling was conducted to remedy these limitations. The results indicated that affect labeling, relative to other forms of encoding, diminished the response of the amygdala and other limbic regions to negative emotional images. Additionally, affect labeling produced increased activity in a single brain region, right ventrolateral prefrontal cortex (RVLPFC). Finally, RVLPFC and amygdala activity during affect labeling were inversely correlated, a relationship that was mediated by activity in medial prefrontal cortex (MPFC). These results suggest that affect labeling may diminish emotional reactivity along a pathway from RVLPFC to MPFC to the amygdala.

If I give it a name it wouldn't be loveIf I give it a name it wouldn't be loveIT WOULDN'T BE LOVE

WASHINGTON (Reuters) - Geese force-fed and then slaughtered for their livers may get their final revenge on people who favor the delicacy known as foie gras: It may transmit a little-known disease known as amyloidosis, researchers reported on Monday.

Tests on mice suggest the liver, popular in French cuisine which uses it to make pate de foie gras and other dishes, may cause the condition in animals that have a genetic susceptibility to such diseases, Alan Solomon of the University of Tennessee and colleagues reported.

That would suggest that amyloidosis can be transmitted via food in a way akin to brain diseases such as Creutzfeldt-Jakob disease, or CJD, which can cause a rare version of mad cow disease in some people who eat affected meat products or brains.

Based on the findings of the study, Solomon and his team concluded that this and perhaps other forms of amyloidosis might be transmissible, like "mad cow" and other related diseases. Until now, no other infectious sources of food products have been found."

"It is not known if there is an increase of Alzheimer’s disease, diabetes or other amyloid-related disease in people who have eaten foie gras," cautioned Solomon. "Our study looked at the existence of amyloid fibrils in foie gras and showed that it could accelerate the development of AA amyloidosis in susceptible mice. Perhaps people with a family history of Alzheimer’s disease, diabetes, rheumatoid arthritis or other amyloid-associated diseases should avoid consuming foie gras and other foods that may be contaminated with fibrils." Other investigators have reported that meat derived from sheep and seemingly healthy cattle may represent other dietary sources of this material, he said.

Morris Sorrells of National Organization of Circumcision Information Resources Center and colleagues created a “penile sensitivity map” by measuring the sensitivity of 19 locations on the penises of 159 male volunteers. Of the participants, 91 were circumcised as infants and none had histories of penile or sexual dysfunction.

For circumcised penises, the most sensitive region was the circumcision scar on the underside of the penis, the researchers found. For uncircumcised penises, the areas most receptive to pressure were five regions normally removed during circumcision—all of which were more sensitive than the most sensitive part of the circumcised penis.

The neuroanatomical definition of homunculus is a "distorted" representation of the sensorimotor body map (and its respective parts) overlaid upon primary somatosensory and primary motor cortices. The above figure illustrates the sensory homunculus, where each body part is placed onto the region of cortex that represents it, and the size of the body part is proportional to its cortical representation (and sensitivity).

Fig 3 (Sorrells et al.): Fine-touch pressure thresholds (g) by location on the adult penis, comparing uncircumcised men (white bars) and circumcised men (gray bars), with a range of one sd shown with the error bars.

The authors' conclusion:

The glans in the circumcised male is less sensitive to fine-touch pressure than the glans of the uncircumcised male. The most sensitive location on the circumcised penis is the circumcision scar on the ventral surface. Five locations on the uncircumcised penis that are routinely removed at circumcision were more sensitive than the most sensitive location on the circumcised penis.

However,

Additional study with vibratory, hot and cold thresholds on a wider variety of positions on the penis is needed.

Poor methods and erroneous statistical analysis mar this paper; e.g. in their Table 2 they fail to compare the same points on the circumcised and uncircumcised penis. Using their data we find no significant differences (Table 1), consistent with previous findings. Only in their multivariate analysis were P values of apparent significance. They claim that several locations on the uncircumcised penis are significantly more sensitive than the most sensitive location on the circumcised penis (the ventral scar), yet their Table 2 shows this applies only to their position 3, the orifice rim of the prepuce. However, after we used the Bonferroni method to correct for multiple comparisons, this significance disappeared. Statistical naiveté is also apparent in their expression of values to up to four significant figures! [gasp!]

And even better! (ibid):

The authors conclude that ‘circumcision ablates the most sensitive parts of the penis’, although they only tested the ability of subjects to detect the lightest touch. Meissner’s corpuscles, being light-touch receptors, would be expected to cause such a measurement to exaggerate the sensitivity of the prepuce. However, sensitivity, particularly when discussing erogenous sensation, depends on several different modes of stimulation and their interaction. In addition, sexual sensation depends upon the types of mechanical stimulation generated during intercourse, which might in turn be influenced by circumcision status. Thus circumcision has the potential to either increase or decrease sexual sensation.Surprisingly, the study omitted to address sexual pleasure. The existence of a market for lidocaine-based products to reduce penile sensitivity attests to the desire by some men for a penis with reduced, not heightened, sensitivity...

I could perhaps reproduce one of the explicit drawings that depict the stimulated regions (including the disputed position 3), but... er..., well, hmm, maybe not. This is a family blog.

OBJECTIVE: To map the fine-touch pressure thresholds of the adult penis in circumcised and uncircumcised men, and to compare the two populations. SUBJECTS AND METHODS: Adult male volunteers with no history of penile pathology or diabetes were evaluated with a Semmes-Weinstein monofilament touch-test to map the fine-touch pressure thresholds of the penis. Circumcised and uncircumcised men were compared using mixed models for repeated data, controlling for age, type of underwear worn, time since last ejaculation, ethnicity, country of birth, and level of education. RESULTS: The glans of the uncircumcised men had significantly lower mean (sem) pressure thresholds than that of the circumcised men, at 0.161 (0.078) g (P = 0.040) when controlled for age, location of measurement, type of underwear worn, and ethnicity. There were significant differences in pressure thresholds by location on the penis (P less than 0.001). The most sensitive location on the circumcised penis was the circumcision scar on the ventral surface. Five locations on the uncircumcised penis that are routinely removed at circumcision had lower pressure thresholds than the ventral scar of the circumcised penis. CONCLUSIONS: The glans of the circumcised penis is less sensitive to fine touch than the glans of the uncircumcised penis. The transitional region from the external to the internal prepuce is the most sensitive region of the uncircumcised penis and more sensitive than the most sensitive region of the circumcised penis. Circumcision ablates the most sensitive parts of the penis.

Wednesday, June 13, 2007

Richard Rorty was an influential modern pragmatist philosopher criticized (unjustly so) by some self-important science types who'd never allow ugly subjectivity to get in the way of their pure pursuit of perfect knowledge. Funny thing is, Rorty could be pretty funny sometimes:

Q: And what would you say to criticisms that your ironism means a kind of sneering-at earnest liberals who don’t want to acknowledge the contingency of their own values?

RR: That was certainly the way it came across. But what I wanted to say was: take yourself with some lightness. Be aware of yourself as at the mercy of the contingencies of your upbringing and your culture and your environment. I thought of it myself as offering advice rather than insults. My liberal ironist doesn’t go around being ironic to everybody she meets. She saves the irony for herself. The liberal part is public and the irony part is private.

Q: Is this [the view that scientists, e.g. physicists, don't know the answers to all of thephilosophical questions that could be asked about physics] a sign of scientists feeling like the philosophical rug is being pulled out from under them?

RR: Yeah, like the priests, they like to think they have a privileged relation to reality. I doubt they do, but one might expect that they would resent it if told they don’t. When the priests of the 19th century were told by practitioners of philological higher criticism of the Bible that they were in the service of middle-eastern creation myths, they didn’t like it. In the middle of this century, the physicists didn’t like it when Kuhn told them they were just trying to solve puzzles.

Speaking of humor, a series of unbelievably silly proposals for nonlethal (but incapacitating) chemical weapons was revealed by the Sunshine Project through a Freedom of Information act (redacted document here).

The US military investigated building a "gay bomb", which would make enemy soldiers "sexually irresistible" to each other, government papers say.

Other weapons that never saw the light of day include one to make soldiers obvious by their bad breath.

. . .

The plan for a so-called "love bomb" envisaged an aphrodisiac chemical that would provoke widespread homosexual behaviour among troops, causing what the military called a "distasteful but completely non-lethal" blow to morale.

Tuesday, June 12, 2007

So I'd like to know where you got the notionSaid I'd like to know where you got the notion

To rock the boatDon't rock the boat babyRock the boat

Don't tip the boat overRock the boatDon't rock the boat babyRock the boat.

Continuing on the topic of nausea and songs from the 70's, the New York Times has an article on mal de débarquement, or "reverse seasickness":

When Seasickness Persists After a Return to Solid GroundBy ELIZABETH SVOBODAPublished: June 12, 2007. . ."Landsickness" or "reverse seasickness" is familiar to many people who have taken long cruises -- once the body has become accustomed to constant motion, the vestibular system, which controls balance, usually takes a few hours or days to acclimate to being on land again. But in patients like Mrs. Josselyn, who suffer from what is known as mal de débarquement, or debarkation sickness, the brain never seems to readapt.Their symptoms, which include dizziness, nausea and a persistent feeling of rocking from side to side, can continue for decades after the fateful voyage that initiates them.... . .After years of treating patients and mulling over individual case histories, Dr. [Timothy C.] Hain has formulated a broad theory of what causes the condition, with the help of Charles Oman, an aeronautics engineer at the Massachusetts Institute of Technology and head of the motion-sickness program at NASA."A very sophisticated way of dealing with your environment is to form an internal model of it in your brain," Dr. Hain said. "A boat is a perfect place for this kind of internal model to form. It's rocking back and forth, and it gets into a rhythm that you start to be able to predict."Sufferers of mal de débarquement, Dr. Hain theorizes, form internal models of the boat that are very accurate — so accurate, in fact, that they typically suffer very little seasickness or uneasiness while on board. "They’re the ones who are walking around the boat and having a great time," he said. "But when they get off, they don’t give up their internal models very easily." The disconnect between the entrenched internal model and the person’s actual surroundings, he believes, is what spawns the disease’s disorienting symptoms.

Friday, June 08, 2007

The area postrema (AP) has been implicated as a chemoreceptor trigger zone for vomiting (emesis) for over 40 years. The AP is located on the dorsal surface of the medulla oblongata at the caudal end of the fourth ventricle. It is one of the so-called circumventricular organs that serve as an interface between the brain parenchyma and the cerebrospinal fluid (CSF)-containing ventricles. The AP lacks a specific blood-brain diffusion barrier to large polar molecules (i.e., a "blood-brain barrier") and is thus anatomically positioned to detect emetic toxins in the blood as well as in the CSF.

CBA is associated with nausea in most readers. However, CBA can induce vomiting in highly sensitive individuals. In an effort to map the neural circuitry of the highly-sensitive variant of CBA, The Neurocritic perused two classic articles on vomiting (Grelot & Miller, 1994; Miller & Leslie, 1994).

from Grelot & Miller (1994)

In general, it appears that CBA falls under the category of Psychogenic Vomiting. Hence, the area postrema is not involved (unless listening to Foreigner, or even the act of imagining listening to Foreigner, results in the release of an emetic substance into the bloodstream). Instead, "higher centers" (i.e., cerebral cortex, limbic system) are likely involved in the highly-sensitive variant of CBA.

So there we have it: "for the first time, researchers have identified neural circuits responsible for Conditioned Blog Aversion (CBA)".

Is anyone else getting tired of articles that use the phrase, "for the first time" for publicity's (or publication in Sci-Nat) sake? For example, take this [unintentionally ironic] press release on déjà-vu:

Neuroscientists at the Picower Institute for Learning and Memory at MIT report in the June 7 early online edition of Science that they have identified for the first time a neuronal mechanism that helps us rapidly distinguish similar, yet distinct, places. The discovery helps explain the sensation of déjà vu.

Or this story:

For the first time, a brain mechanism has been identified that helps us distinguish similar, yet distinct, places. This discovery helps researchers explain the sensation of déjà vu and could lead to treatments for memory-related disorders. It may also help scientists with finding more effective treatments for the confusion and disorientation that afflict senior citizens who have trouble distinguishing between separate but similar places and experiences.

Forming distinct representations of multiple contexts, places and episodes is a crucial function of the hippocampus. The dentate gyrus subregion has been suggested to fulfill this role. We have tested this hypothesis by generating and analyzing a mouse strain that lacks the gene encoding the essential subunit of the N-methyl-D-aspartate (NMDA) receptor, NR1, specifically in dentate gyrus granule cells. The mutant mice performed normally in contextual fear conditioning, but were impaired in the ability to distinguish two similar contexts. A significant reduction in the context-specific modulation of firing rate was observed in the CA3 pyramidal cells when the mutant mice were transferred from one context to another. These results provide evidence that NMDA receptors in the granule cells of the dentate gyrus play a crucial role in the process of pattern separation.

I don't have access to the pdf, so I can't say too much more, except...

Fill my eyes with that double vision, no disguise for that double visionOoh, when it gets through to me, its always new to meMy double vision gets the best of me

About Me

Born in West Virginia in 1980, The Neurocritic embarked upon a roadtrip across America at the age of thirteen with his mother. She abandoned him when they reached San Francisco and The Neurocritic descended into a spiral of drug abuse and prostitution. At fifteen, The Neurocritic's psychiatrist encouraged him to start writing as a form of therapy.